1. Field of the Invention
The present invention relates to a method and device for tracing leaks in vivo in an electrode device, such as for a pacemaker or a defibrillator, the electrode device being of the type having an electrode cable containing an elongate, flexible conductor whose exterior is covered with a layer of insulation and whose interior forms a channel.
2. Description of the Prior Art
Tracing leaks in electrode devices including a cable of the type described above, which are not yet implanted in a patient, is conventionally accomplished with the aid of a compressed air device connected to the orifice of the electrode cable's interior channel. Air is then forced into the channel so a gauge pressure develops and the electrode cable is immersed in water. If the cable is defective, air seeps out of the channel through the leak(s), and air bubbles appear in the water, thereby indicating presence of the leak(s).
When an implanted system, consisting of a pacemaker and an attendant pacemaker electrode, starts producing, e.g., poor threshold values or falling values for impedance, the physician may suspect the cause to be a defective pacemaker or a leak in the electrode cable, enabling body fluids to penetrate into the channel and come into contact with any non-insulated conductor. Such a leak could develop in conjunction with the introduction of the pacemaker electrode through a vein into the patient's heart, such introduction generally being performed with the aid of a relatively stiff stylet. It is not uncommon for the stylet, during introduction into the electrode cable's interior channel or when displaced in the channel, to penetrate both the conductor, which generally forms the channel, as well as the outer layer of insulation. A leak can also develop when the insulation becomes fatigued or abraded. In fluoroscopic examination of a patient with an implanted pacemaker electrode, an experienced physician or radiologist can discern a break in a conductor. Identifying a leak in the layer of insulation is, however, impossible. After having determined that the pacemaker is not at fault, the physician was therefore left with no choice but to replace the implanted electrode cable with another, without knowing for certain whether the electrode cable's layer of insulation was defective. Such certainty was also impossible to achieve when the physician explanted the electrode device, since the cable is generally damaged in the explantation procedure.